because they carry rat lungworm parasites - and the species is crawling in North Carolina The parasite-infested Apple Snail, an invasive species native to South America, has been creeping up the desert southwest and the eastern seaboard, with state wildlife authorities now sounding the alarm in North Carolina. The snails are known to be vectors for rat lungworm — which can endanger dogs with symptoms that start with hind-leg weakness, followed by hind-leg paralysis, and can progress up the canine body, ultimately to brain damage.